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When it comes to installing solar power systems in typical apartment buildings in Korea, which represent 60% of overall houses, we note that apartments are not ideal for getting the best performance out of solar panels. Still, local governments have been seeking to expand solar installations. For instance, the Seoul metropolitan government has been offering solar-related subsidies since it embarked on a project to encourage installations of small-sized solar systems in the 2010s. The ratio of subsidies to installation costs has risen from 50% in 2015 to 78% in 2020. Installations of solar modules (325W), micro inverters, and monitoring systems currently cost W500,000 on average, with subsidies of W400,000 provided by the Seoul metropolitan government. With an additional subsidy of W50,000~100,000 offered by regional offices, installations of solar systems cost less than W100,000. Of note, five years of free after-service are included, with support for product liability insurance also being offered.
Solar panel installation costs plunging
Installation costs for building-mounted solar systems for use in apartments have also been declining thanks to falling solar panel prices. Given such, the average installation cost has fallen 42% from W2,640/1KW in 2015 to W1,539/1KW in 2020. The actual cost borne by consumers has plunged 75% from W1,320/1KW to W339/1KW. According to the Seoul metropolitan government, the installation of a 260W solar system will lead to an annual power bill saving of W64,200 for a household with power consumption of 304kWh per month.
Optimum installation angles not applicable to building-mounted solar panels at apartments
We have looked at economic effects that households should see via installations of building-mounted solar panels at apartments. Assuming that a four-person household installs a 325W capacity solar system, if subtracting subsidies of W390,000 from total installation costs, actual costs borne by the household should total W110,000.
Of note, the optimum angle for solar installations is typically observed between azimuth angles of -30Â°~+50Â°, with a pitch angle of 10Â°~30Â°. But, it is challenging to satisfy the above-noted optimum angle requirements when installing solar panels on balcony railings, where solar panels for use in apartments are most often found.
Utilization rate of 10% estimated for building-mounted solar panels at apartments
In order to gauge the power generation efficiency of building-mounted solar panels at apartments, we assume an azimuth angle of between -50Â°~-30Â° and +50Â°~+80Â° and a pitch angle of 50Â°~70Â°. We have also assumed that energy efficiency could vary, depending on solar elevation angles. All considered, when mounted on apartment buildings, a 325W solar panel produces electricity of 282kWh pa, with the utilization rate coming to 10%. But, when mounted on the ground, such a panel generates 439kWh pa at a utilization rate of 15%. In other words, annual power production of building-mounted panels at apartments is estimated to be 35% lower than that for panels installed under optimum conditions. Of note, effects from variations in precipitation have not been considered. Still, our comparison suggests that solar panels mounted on apartment buildings are not as efficient as those mounted on the ground.
It is challenging to exactly predict power demand from home appliances
We note that refrigerators operate 24/7 but show irregular power consumption patterns, as their inverter compressors run whenever cooling is required to maintain a certain temperature. As power consumption varies by individual device, it is difficult to exactly predict power demand from home appliances such as refrigerators. Meanwhile, over 12:00~16:00, when power generation from solar panels is high, power consumption at households tends to be lowâ€”a factor that typically leaves a large portion of power supply from solar systems unused. Given this backdrop, directing the power generated from building-mounted solar systems at apartments towards home appliances (whose power demand is difficult to predict) is likely to generate inefficiencies. Of note, while solar panels mounted on apartment buildings generate an average of 282kWh of electricity pa (utilization rate of 10%), when directing the generated power towards home appliances only, the de facto power supply (ie, the amount after subtracting the unused power) should come to 218kWh (utilization rate of 8%).
Still, solar systems at apartments lead to bill savings of W45,000 pa
Assuming 24/7 operation for refrigerators and 24-hour operation for air purifiers in spring/autumn and 12-hour operation in winter, with air conditioner temperatures set at 28Â°C, we arrive at electricity usage of 372kWh per month, leading to average monthly bills of around W55,000 (W660,000 pa). But, the amount slides to W51,500 (W618,000 pa) when using solar power systems. All in all, while using solar systems at apartments may not be as efficient as hoped, it still leads to significant power bill savings.